Multi-level liquid level magnetic sensor

a magnetic sensor and liquid level technology, applied in liquid/fluent solid measurement, instruments, machines/engines, etc., can solve the problems of cost and reliability problems of a multiple float system, and achieve the effect of expanding the operating range of a single floa
US20110138907A1Inactive Publication Date: 2011-06-16ILLINOIS TOOL WORKS INC
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
ILLINOIS TOOL WORKS INC
Publication Date
2011-06-16
Estimated Expiration
Not applicable · inactive patent

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Abstract

A liquid level sensor employs a set of axially displaced magnetic sensing switches and a magnet on a float that may rise and fall on liquid level to activate and deactivate the switches. The switches and magnet are configured so that movement of the magnetic float activates a new switch before deactivation of an adjacent previously activated switch. An electronic circuit provides a signal based on the uppermost activated switch to provide a signal that is monotonic with liquid level. The design may be readily implemented using reed switches and a resistive ladder.
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Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This Non-Provisional Application claims benefit to U.S. Provisional Application Ser. No. 61 / 057,073 filed May 29, 2008 hereby incorporated by reference.FIELD OF THE INVENTION

[0002] The present invention relates to fluid level sensors, particularly sensors that may be suitable for use in monitoring urea levels in diesel engine emission control systems using “selective catalytic reduction” (SCR).BACKGROUND OF THE INVENTION

[0003] A wide variety of liquid level sensing technologies exist including those using ultrasonic signals, changes in capacitance, and changes in electrical resistance. One type of liquid level sensor employs magnetic reed switches arranged along a column. The reed switches close in the proximity of a magnetic field which may be produced by a magnet held in a float rising and falling with the liquid level. In order to provide a continuous output signal that changes monotonically (that is, always increases and never decreases ...

Claims

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